Hydrogenation catalyst and process for producing olefin polymer

ABSTRACT

The purpose of the present invention is to provide a hydrogenation catalyst, which can produce an olefin polymer having a higher molecular weight, and a process for producing an olefin polymer so that an olefin polymer having a higher molecular weight can be produced, by controlling hydrogen concentration in a polymerization reaction system efficiently in polymerizing an olefin in the presence of hydrogen. There is provided a hydrogenation catalyst formed by contacting the undermentioned component (A), the undermentioned component (B), and the undermentioned component (C). There is further provided a process for producing an olefin polymer characterized by polymerizing an olefin in the presence of hydrogen, the undermentioned component (A), the undermentioned component (B), and the undermentioned component (D).
     Component (A): a titanocene compound   Component (B): a silicon compound represented by the undermentioned general formula [1]   

       Si(OR 1 ) 4   [1] 
     (In the formula, R 1  stands for a hydrocarbon group having 1 to 20 carbon atoms, and four R 1  may be same or different respectively.)
     Component (C): an alkyl metal compound   Component (D): a catalyst for olefin polymerization

FIELD OF THE INVENTION

The present invention relates to a hydrogenation catalyst and a processfor producing an olefin polymer.

BACKGROUND OF THE INVENTION

Heretofore, in a process for producing an olefin polymer by use of gasphase polymerization reaction in the presence of hydrogen, there hasbeen known a method for controlling hydrogen concentration within a gasphase polymerization reaction vessel, which comprises lowering hydrogenconcentration within the gas phase polymerization reaction vessel bytaking out a portion of a hydrogen-containing gas within the gas phasepolymerization reaction vessel, then adding hydrogen in the gas takenout to an olefin to hydrotreat the gas, and thereafter feeding thehydrotreated gas again to the polymerization reaction vessel. (Refer to,for example, Patent Document 1.)

Furthermore, in a process for producing an olefin polymer in thepresence of hydrogen, there has been known a method for controllingmolecular weight distribution or the like of the olefin polymer producedby adding a hydrogenation catalyst to a reaction vessel to lowerhydrogen concentration. (Refer to, for example, Patent Document 2.)

[Patent Document 1]JP-A-10-204123

[Patent Document 2]JP-A-8-151408

BRIEF SUMMARY OF THE INVENTION

However, in the method for controlling hydrogen concentration disclosedin the above Patent Document 1, it was necessary to provide a reactionlayer separately in order to use a hydrogenation catalyst, and there wasthe problem that clogging of the reaction layer or a circulating gasline or deterioration of catalyst performance was caused.

Furthermore, in the method of adding a hydrogenation catalyst to areaction vessel as disclosed in the above Patent Document 2, there werethe problems that a large amount of a hydrogenation catalyst wasnecessary, and that hydrogen concentration could not be sufficientlylowered.

In view of such current situation, the purpose of the present inventionresides in providing a hydrogenation catalyst, which can produce anolefin polymer having a higher molecular weight, and a process forproducing an olefin polymer so that an olefin polymer having a highermolecular weight can be produced, by controlling hydrogen concentrationin a polymerization reaction system efficiently in polymerizing anolefin in the presence of hydrogen.

The present inventors have devoted themselves to study for solving theabove problems. As a result, they have found that by adding a titanocenecompound and a specific silicon compound in a polymerization reactionsystem, hydrogen concentration in the polymerization reaction system canbe lowered efficiently and an olefin polymer having a higher molecularweight can be produced, and have led to accomplishment of the presentinvention.

That is, the present invention relates to a hydrogenation catalystformed by contacting the undermentioned component (A), theundermentioned component (B), and the undermentioned component (C).

Component (A): a titanocene compoundComponent (B): a silicon compound represented by the undermentionedgeneral formula [1]

Si(OR¹)₄  [1]

In the formula, R¹ stands for a hydrocarbon group having 1 to 20 carbonatoms. Four R¹ may be same or different respectively.

Component (C): an alkyl metal compound

Furthermore, the present invention relates to a process for producing anolefin polymer characterized by polymerizing an olefin in the presenceof hydrogen, the undermentioned component (A), the undermentionedcomponent (B), and the undermentioned component (D).

Component (A): a titanocene compoundComponent (B): a silicon compound represented by the undermentionedgeneral formula [1]

Si(OR¹)₄  [1]

In the formula, R¹ stands for a hydrocarbon group having 1 to 20 carbonatoms. Four R¹ may be same or different respectively.Component (D): a catalyst for olefin polymerization

Moreover, the present invention relates to a process for producing anolefin polymer, which comprises polymerizing an olefin in the presenceof hydrogen and the undermentioned component (D), characterized byhaving a step of adding the undermentioned component (A) into apolymerization reaction system and a step of adding the undermentionedcomponent (B).

Component (A): a titanocene compoundComponent (B): a silicon compound represented by the undermentionedgeneral formula [1]

Si(OR¹)₄  [1]

In the formula, R¹ stands for a hydrocarbon group having 1 to 20 carbonatoms. Four R¹ may be same or different respectively.

Component (D): a catalyst for olefin polymerization

In addition, the present invention relates to a process for producing anolefin polymer, which comprises having two or more olefin polymerizationsteps different in olefin polymerization conditions and polymerizing anolefin in the presence of hydrogen and the undermentioned component (D),characterized by having a step of adding the undermentioned component(A) and a step of adding the undermentioned component (B) into apolymerization reaction system in the second and subsequent olefinpolymerization steps.

Component (A): a titanocene compoundComponent (B): a silicon compound represented by the undermentionedgeneral formula [1]

Si(OR¹)₄  [1]

In the formula, R¹ stands for a hydrocarbon group having 1 to 20 carbonatoms. Four R¹ may be same or different respectively.

Component (D): a catalyst for olefin polymerization

ADVANTAGES OF THE INVENTION

According to the present invention, in a process for producing an olefinpolymer, which comprises polymerizing an olefin in the presence ofhydrogen, hydrogen concentration in a polymerization reaction system canbe controlled efficiently and an olefin polymer having a highermolecular weight can be produced.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention is explained in more detail.

1) Hydrogenation Catalyst

The hydrogenation catalyst is a catalyst having capability tohydrogenate selectively olefinic unsaturated double bonds, and hydrogenpresent in a polymerization reaction vessel reacts with an olefin suchas propylene, ethylene or the like and is removed as propane or ethane.

The hydrogenation catalyst of the present invention is characterized bybeing formed by contacting the undermentioned component (A), theundermentioned component (B), and the undermentioned component (C).

Component (A): a titanocene compoundComponent (B): a silicon compound represented by the undermentionedgeneral formula [1]

Si(OR¹)₄  [1]

In the formula, R¹ stands for a hydrocarbon group having 1 to 20 carbonatoms. Four R¹ may be same or different respectively.

Component (C): an alkyl metal compound

As a titanocene compound of component (A), a titanocene compoundrepresented by the undermentioned general formula [3] is preferable.

Cp_(n)TiX¹ _(4-n)  [3]

In the formula, Cp stands for a group selected from substituted orunsubstituted cyclopentadienyl group, indenyl group, or fluorenyl group,X¹ stands for a group selected from hydrogen, halogen, alkoxy group,amino group, alkyl group having 1 to 10 carbons, or aryloxy group, and nstands for an integer of 1 to 3. The respective ligands may be bondedtogether through a crosslinking group.

Among them, a biscyclopentadienyl compound having two cyclopentadienylgroups is preferable.

Specifically, there are cited bis(cyclopentadienyl)titanium dichloride,bis(cyclopentadienyl)titanium dibromide, bis(cyclopentadienyl)titaniumdiiodide, bis(cyclopentadienyl)titanium difluoride,bis(cyclopentadienyl)titanium chlorobromide,bis(cyclopentadienyl)titanium methoxychloride,bis(cyclopentadienyl)titanium ethoxychloride,bis(cyclopentadienyl)titanium phenoxychloride,bis(cyclopentadienyl)titanium dimethoxide, bis(cyclopentadienyl)titaniumdiphenoxide, and the like.

They may be used singly or in a combination of two or more kinds.

The silicon compound represented by the above-mentioned general formula[1]of component (B) specifically includes tetramethoxysilane,tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane,tetrabenzyloxysilane, dimethoxydiethoxysilane, diethoxydipropoxysilane,diethoxydibutoxysilane, methoxytriethoxysilane, andethoxytripropoxysilane. Among them, tetramethoxysilane,tetraethoxysilane, and tetrapropoxysilane.

They may be used singly or in a combination of two or more kinds.

The molar ratio of silicon atom of component (B) and titanium atom ofcomponent (A) is preferably 1:1 to 10000:1, more preferably 10:1 to1000:1, and further more preferably 100:1 to 500:1.

The alkyl metal compound of component (C) includes, for example, alkylaluminum compound, alkyl lithium compound, alkyl magnesium compound,alkyl zinc compound, and the like. Among them, use in combination withan alkyl aluminum compound is preferable.

The above alkyl aluminum compound includes, for example, trialkylaluminum, alkyl aluminum halide, alkyl aluminum hydride, aluminumalkoxide, almoxane, and the like.

A trialkyl aluminum includes, for example, trimethyl aluminum, triethylaluminum, triisobutyl aluminum, trihexyl aluminum, trioctyl aluminum,tridecyl aluminum, and the like.

An alkyl aluminum halide includes, for example, diethyl aluminummonochloride, diisobutyl aluminum monochloride, ethyl aluminumsesquichloride, ethyl aluminum dichloride, and the like.

An alkyl aluminum hydride includes, for example, diethyl aluminumhydride, diisobutyl aluminum hydride, and the like.

An aluminum alkoxide includes, for example, diethyl aluminum ethoxide,diethyl aluminum phenoxide, and the like.

An almoxane includes, for example, methyl almoxane, ethyl almoxane,isobutyl almoxane, methylisobutyl almoxane, and the like.

Among them, a trialkyl aluminum is preferable, and triethyl aluminum ismore preferable.

They may be used singly or in a combination of two or more kinds.

The molar ratio of metal atoms of an alkyl metal compound and atitanocene compound is preferably 1:1 to 30:1, more preferably 2:1 to10:1, and further more preferably 3:1 to 7:1.

The hydrogenation catalyst of the present invention can be favorablyused for controlling hydrogen concentration in a polymerization reactionsystem efficiently and producing an olefin polymer having a highermolecular weight in a process for producing an olefin polymer, whichcomprises polymerizing an olefin in the presence of hydrogen.

With regard to component (A), component (B) and component (C) used inthe hydrogenation catalyst of the present invention, in a process forproducing an olefin polymer mentioned later, a product formed bycontacting two or more components of component (A), component (B) andcomponent (C) in advance may be added in a polymerization reactionvessel, or respective components of component (A), component (B) andcomponent (C) may be separately added in a polymerization reactionvessel.

2) Process for Producing Olefin Polymer

The process for producing an olefin polymer of the present invention ischaracterized by polymerizing an olefin in the presence of hydrogen, theabove-mentioned component (A), the above-mentioned component (B), andthe undermentioned component (D).

Component (D): a catalyst for olefin polymerization

As the catalyst for olefin polymerization of component (D), there can beused publicly known polymerization catalysts used for olefinpolymerization, and there can be cited Ziegler-Natta catalysts, whichare disclosed in, for example, JP-A-57-63310, JP-A-58-83006,JP-A-61-78803, JP-A-7-216017, JP-A-10-212319, JP-A-62-158704, andJP-A-11-92518, or metallocene type catalysts, which are disclosed inJP-A-5-155930, JP-A-9-143217, JP-A-2002-293817, JP-A-2003-171412,JP-A-8-511044, and JP-A-2001-31720.

Ziegler-Natta catalysts are preferably materials formed by contactingthe undermentioned component (a) and the undermentioned component (b),and more preferably materials formed by contacting the undermentionedcomponent (a), the undermentioned component (b), and the undermentionedcomponent (c): component (a): a solid component containing titanium,magnesium and a halogen,

component (b): an alkyl aluminum compound, and component (c): anelectron-donating compound.

As examples of a method for preparing the component (a), there can beshown the following methods (1) to (5):

(1) a method of contacting a halogenated magnesium compound and atitanium compound,(2) a method of contacting a halogenated magnesium compound, an electrondonor, and a titanium compound,(3) a method of dissolving a halogenated magnesium compound and atitanium compound in an electron-donating solvent to obtain a solutionand then impregnating the solution into a carrier material,(4) a method of contacting a dialkoxy magnesium compound, a halogenatedtitanium compound, and an electron donor, and(5) a method of contacting a solid component containing magnesium atom,titanium atom, and a hydrocarbon oxy group, a halogenated compound, andan electron donor and/or an organic acid halide.

Among them, the solid component obtained by the method of (5) ispreferable, and the solid component containing a phthalic acid estercompound as an electron donor is more preferable.

An alkyl aluminum compound of component (b) includes, for example,trialkyl aluminum, alkyl aluminum halide, alkyl aluminum hydride,aluminum alkoxide, almoxane, and the like.

A trialkyl aluminum includes, for example, trimethyl aluminum, triethylaluminum, triisobutyl aluminum, trihexyl aluminum, trioctyl aluminum,tridecyl aluminum, and the like.

An alkyl aluminum halide includes, for example, diethyl aluminummonochloride, diisobutyl aluminum monochloride, ethyl aluminumsesquichloride, ethyl aluminum dichloride, and the like.

An alkyl aluminum hydride includes, for example, diethyl aluminumhydride, diisobutyl aluminum hydride, and the like.

An aluminum alkoxide includes, for example, diethyl aluminum ethoxide,diethyl aluminum phenoxide, and the like.

An almoxane includes, for example, methyl almoxane, ethyl almoxane,isobutyl almoxane, methylisobutyl almoxane, and the like.

Among them, a trialkyl aluminum is preferable, and triethyl aluminum ismore preferable.

They may be used singly or in a combination of two or more kinds.

As an electron-donating compound of component (c), there is preferablyused a silicon compound represented by the following general formula[2]:

R² _(r)Si(OR³)_(4-r)  [2]

wherein R² stands for hydrogen atom, a hydrocarbon group having 1 to 20carbon atoms, or a hetero atom-containing group, R³ stands for ahydrocarbon group having 1 to 20 carbon atoms, and r stands for aninteger of 0 to 3, and when plural R² are present, plural R² may berespectively same or different, and when plural R³ are present, pluralR³ may be respectively same or different.

A hydrocarbon group having 1 to 20 carbon atoms of R² includes, forexample, straight chain alkyl group having 1 to 20 carbon atoms,branched chain alkyl group having 1 to 20 carbon atoms, cycloalkyl grouphaving 1 to 20 carbon atoms, cycloalkenyl group having 1 to 20 carbonatoms, aryl group having 1 to 20 carbon atoms, and the like.

A straight chain alkyl group having 1 to 20 carbon atoms includes, forexample, methyl group, ethyl group, propyl group, butyl group, pentylgroup, and the like.

A branched chain alkyl group having 1 to 20 carbon atoms includes, forexample, isopropyl group, sec-butyl group, tert-butyl group, tert-amylgroup, and the like.

A cycloalkyl group having 1 to 20 carbon atoms includes, for example,cyclopentyl group, cyclohexyl group, and the like.

A cycloalkenyl group having 1 to 20 carbon atoms includes, for example,cyclopentenyl group, and the like.

An aryl group having 1 to 20 carbon atoms includes for example, phenylgroup, tolyl group, and the like.

A hetero atom-containing group of R² includes, for example, oxygenatom-containing group, nitrogen atom-containing group, sulfuratom-containing group, phosphorus atom-containing group, and the like.Specifically, there are cited dialkylamino group such as dimethylaminogroup, methylethylamino group, diethylamino group, ethyl-n-propylaminogroup, or di-n-propylamino group, pyrrolyl group, pyridyl group,pyrrolidinyl group, piperidyl group, perhydroindolyl group,perhydroisoindolyl group, perhydroquinolyl group, perhydroisoquinolylgroup, perhydrocarbazolyl group, perhydroacrydinyl group, furyl group,pyranyl group, perhydrofuryl group, thienyl group, and the like. Amongthem, preferable is a group having a hetero atom which can bond directlyto the silicon atom of a silicon compound.

A hydrocarbon group having 1 to 20 carbon atoms of R³ includes thosewhich are same as the examples shown as a hydrocarbon group having 1 to20 carbon atoms of R².

A preferable electron-donating compound is a silicon compound having asR² at least one hydrocarbon group having a secondary or tertiary carbonatom bonded directly to silicon atom or at least one dialkylamino groupin the above-mentioned general formula [2].

Preferable concrete examples of an electron-donating compound includediisopropyldimethoxysilane, di-tert-butyldimethoxysilane,tert-butylmethyldimethoxysilane, tert-butylethyldimethoxysilane,tert-butyl-n-propyldimethoxysilane, tert-butyl-n-butyldimethoxysilane,tert-amylmethyldimethoxysilane, tert-amylethyldimethoxysilane,tert-amyl-n-propyldimethoxysilane, tert-amyl-n-butyldimethoxysilane,isobutylisopropyldimethoxysilane, tert-butylisopropyldimethoxysilane,dicyclobutyldimethoxysilane, cyclobutylisopropyldimethoxysilane,cyclobutylisobutyldimethoxysilane, cyclobutyl-tert-butyldimethoxysilane,dicyclopentyldimethoxysilane, cyclopentylisopropyldimethoxysilane,cyclopentylisobutyldimethoxysilane,cyclopentyl-tert-butyldimethoxysilane, dicyclohexyldimethoxysilane,cyclohexylmethyldimethoxysilane, cyclohexylethyldimethoxysilane,cyclohexylisopropyldimethoxysilane, cyclohexylisobutyldimethoxysilane,cyclohexyl-tert-butyldimethoxysilane,cyclohexylcyclopentyldimethoxysilane, cyclohexylphenyldimethoxysilane,diphenyldimethoxysilane, phenylmethyldimethoxysilane,phenylisopropyldimethoxysilane, phenylisobutyldimethoxysilane,phenyl-tert-butyldimethoxysilane, phenylcyclopentyldimethoxysilane,diisopropyldiethoxysilane, diisobutyldiethoxysilane,di-tert-butyldiethoxysilane, tert-butylmethyldiethoxysilane,tert-butylethyldiethoxysilane, tert-butyl-n-propyldiethoxysilane,tert-butyl-n-butyldiethoxysilane, tert-amylmethyldiethoxysilane,tert-amylethyldiethoxysilane, tert-amyl-n-propyldiethoxysilane,tert-amyl-n-butyldiethoxysilane, dicyclopentyldiethoxysilane,dicyclohexyldiethoxysilane, cyclohexylmethyldiethoxysilane,cyclohexylethyldiethoxysilane, diphenyldiethoxysilane,phenylmethyldiethoxysilane, 2-norbornane-methyldimethoxysilane,bis(perhydroquinolino)dimethoxysilane,bis(perhydroisoquinolino)dimethoxysilane,(perhydroquinolino)(perhydroisoquinolino)dimethoxysilane,(perhydroquinolino)methyldimethoxysilane,(perhydroisoquinolino)methyldimethoxysilane,(perhydroquinolino)ethyldimethoxysilane,(perhydroisoquinolino)ethyldimethoxysilane,(perhydroquinolino)(n-propyl)dimethoxysilane,(perhydroisoquinolino)(n-propyl)dimethoxysilane,(perhydroquinolino)(tert-butyl)dimethoxysilane,(perhydroisoquinolino)(tert-butyl)dimethoxysilane, anddiethylaminotriethoxysilane.

They may be used singly or in a combination of two or more kinds.

When a metallocene type catalyst is used as a catalyst for olefinpolymerization, as a metallocene compound, preferable is a metallocenecompound represented by the following general formula [4]:

Cp_(n)MX_(4-n)  [4]

wherein Cp is a group selected from substituted or unsubstitutedcyclopentadienyl group, indenyl group, or fluorenyl group, M is anelement selected from zirconium and hafnium, X is a group selected fromhydrogen, halogen, alkoxy group, amino group, alkyl group having 1 to 10carbons, or aryloxy group, plural Cps and Xs may be bonded togetherthrough a crosslinking group, and n stands for an integer of 1 to 3.

In the process for producing an olefin polymer of the present invention,it is preferable to polymerize olefin in the presence of hydrogen, theabove-mentioned component (A), the above-mentioned component (B), theabove-mentioned component (C), and the above-mentioned component (D).

[Polymerization Steps]

The process for producing an olefin polymer of the present invention canbe applied to not only batch polymerization process but also continuouspolymerization process. In addition, when, for example, a metallocenetype catalyst is used as a catalyst for olefin polymerization, in manycases the resulting olefin polymers have unsaturated bonds at theirterminals. It appears that such unsaturated bonds would be formed bydehydrogenation of the saturated terminals once produced, and thereforethere is the possibility that such hydrogen would be graduallyconcentrated in a circulating olefin. Thus, in such a case, the presentinvention can be applied as a technique for controlling the hydrogenconcentration in a single polymerization step.

Furthermore, in some cases the present invention is necessary also in amultistage polymerization having plural polymerization steps differentin polymerization conditions. In a multistage polymerization,polymerization may be carried out by changing polymerization conditionsin a single reaction vessel, or polymerization may be carried out inplural reaction vessels different in polymerization conditions, whichare connected in series. The present invention can be applied, whenhydrogen concentration in the subsequent stage is lowered efficiently ascompared with the precedent stage in a single reaction vessel, or inorder to efficiently lower hydrogen flowing with powders from theprecedent stage reaction vessel into the subsequent stage reactionvessel in a multistage polymerization using plural reaction vessels.

Therefore, in the process for producing an olefin polymer of the presentinvention, as long as an olefin can be polymerized in the presence ofhydrogen, a single stage polymerization using single polymerizationconditions may be carried out or a multistage polymerization consistingof plural polymerization steps different in polymerization conditionsmay be carried out, and polymerization may be carried out by use of asingle reaction vessel or polymerization may be carried out by use ofplural reaction vessels. Herein, polymerization conditions meanpolymerization form, temperature, pressure, raw material composition,and the like, and polymerization form means liquid phase polymerizationor gas phase polymerization. When a multistage polymerization is used,liquid phase polymerization and gas phase polymerization may be used incombination. Liquid phase polymerization means bulk polymerization orslurry polymerization, and gas phase polymerization means mixing vesseltype gas phase polymerization, fluidized bed type gas phasepolymerization, or entrained bed type gas phase polymerization.

In the process for producing an olefin polymer of the present invention,when excess alkyl aluminum compound is used for a catalyst for olefinpolymerization of component (D), the excess alkyl aluminum compound hasan effect similar to that of an alkyl metal compound of component (C),and hence in such a case component (C) need not be further added.

Furthermore, in the process for producing an olefin polymer of thepresent invention, component (A), component (B), and, as needed,component (C) may be present in a polymerization reaction vessel beforeinitiation of olefin polymerization, or a step of adding component (A),a step of adding component (B), and, as needed, a step of addingcomponent (C) may be present in the stage of growth process of an olefinpolymer.

Moreover, in the case of a multistage polymerization having two or moreolefin polymerization steps different in olefin polymerizationconditions, it is preferable to add component (A), component (B), and,as needed, component (C) in the second and subsequent olefinpolymerization steps.

In addition, the process for producing an olefin polymer of the presentinvention is carried out preferably by use of a gas phase reactionvessel. As the gas phase reaction vessel, preferable is a fluidized bedtype one wherein a gas is flown vertically and upwardly in a cylindricalreaction vessel provided with a gas-dispersing board.

With regard to the addition place of component (A), component (B), and,as needed, component (C), when they are added in a gas phase reactionvessel, they are preferably added to a bed portion thereof. The bedportion means a powder-concentrated portion having a bulk density ofpolymerized powder of not less than 0.10 g/cc in a gas phase reactionvessel. In the present invention, preferably component (A), component(B), and, as needed, component (C) are added to a bed portion having abulk density of polymerized powder of not less than 0.13 g/cc and notmore than 0.70 g/cc, and more preferably component (A), component (B),and, as needed, component (C) are added to a bed portion having a bulkdensity of polymerized powder of not less than 0.16 g/cc and not morethan 0.50 g/cc.

The addition place of component (A), component (B), and, as needed,component (C) in a fluidized bed type gas phase polymerization ispreferably within a bed portion formed just above a dispersing board,from the standpoint of mixing a polymer and the respective componentssufficiently and increasing hydrogenation performance. When the heightof a dispersing board is presumed as 0 and the height of a bed portionis presumed as H, these components are preferably added to a portionhaving a height of 0 to 0.5H and most preferably added to a portionhaving a height of 0 to 0.3H.

With regard to the amount of a titanocene compound charged, the molaramount of titanium atom in a titanocene compound to 1 kg of polymerizedpowders in a reaction vessel (mmol/kg) is preferably not less than0.0001 mmol/kg and not more than 1 mmol/kg, more preferably not lessthan 0.0003 mmol/kg and not more than 0.5 mmol/kg, and most preferablynot less than 0.001 mmol/kg and not more than 0.1 mmol/kg.

Component (A), component (B), and, as needed, component (C) may becharged continuously or intermittently in a reaction vessel.

Component (A) can be fed after diluted with an inert organic solvent. Inso doing, as component (A) a product (component (A′)) formed bycontacting it with component (C) in advance may be used. The above inertorganic solvent means a solvent that does not react with any materialparticipating in hydrogenation reaction. As a preferable solvent, thereare cited aliphatic hydrocarbons such as butane, pentane, hexane,heptane, octane and the like, and the isomers thereof, andcycloaliphatic hydrocarbons such as cyclohexane, cycloheptane and thelike, and the derivatives thereof.

[Main Polymerization]

In the process for producing an olefin polymer of the present invention,an olefin polymer produced in a reaction vessel may be a homopolymer ora copolymer. As examples of an olefin to be polymerized in the presentinvention, there can be shown ethylene, propylene, 1-butene, 1-pentene,1-hexene, 1-octene, 1-decene, 4-methyl-1-pentene, 3-methyl-1-pentene,styrene, butadiene, isoprene, 1,4-hexadiene, dicyclopentadiene,5-ethylidene-2-norbornene, and the like, and the olefin is determineddepending on the kind of the desired polymer product. That is, when, forexample, polyethylene, polypropylene, polybutene and the like areproduced as a homopolymer product, and EPR (ethylene-propylenecopolymer), PBR (propylene-butene copolymer), EPBR(ethylene-propylene-butene copolymer) and the like are produced as acopolymer product, olefins to be used in polymerization steps areethylene, propylene, and butene, and in some cases an extremely smallamount of the other olefins are used.

In the case of multistage polymerization, the same polymer may beproduced in each stage, or polymers different in compositions may beproduced. In case the same polymer is produced in each stage, a hydrogencontent in the subsequent stage gas phase reactor can be decreased byadding the above component (A) and the above component (B) into thesubsequent stage polymerization reaction system, and thus an olefinpolymer having a broad molecular weight distribution, in which a polymerproduced in the subsequent stage has a molecular weight higher than thatof a polymer produced in the precedent stage, can be produced.Additionally, in case polymers different in compositions are produced ineach stage, the present invention can be used in the production of anolefin polymer which contains a polymer having a lower molecular weightproduced in the precedent stage and a polymer having a higher molecularweight produced in the subsequent stage and having a compositiondifferent from that of the precedent stage.

The process for producing an olefin polymer of the present invention ispreferably a process for producing an ethylene-propylene block copolymercomprising a first polymerization step of polymerizing propylene in thepresence of hydrogen and the above component (D) to obtain a propylenehomopolymer and a second polymerization step of polymerizing ethyleneand propylene in the presence of the propylene homopolymer obtained inthe first polymerization step to obtain an ethylene-propylene copolymer,further comprising the steps of adding the above component (A) and theabove component (B) into the reaction system of the above secondpolymerization step.

In the above process for producing an ethylene-propylene blockcopolymer, the ratio of the limiting viscosity of the propylenehomopolymer obtained in the first polymerization step to the limitingviscosity of the ethylene-propylene copolymer obtained in the secondpolymerization step is preferably 2 to 20, more preferably 2.5 to 15,and further preferably 3.5 to 10.

The first polymerization step and/or the second polymerization step maybe a single-stage polymerization step or a multistage polymerizationstep.

Polymerization temperature is different depending on the kind of amonomer, the molecular weight of a product, and the like, but is notmore than the melting point of an olefin polymer, preferably lower by10° C. or more than the melting point, more preferably room temperatureto 200° C., specially preferably 40 to 160° C., and most preferably 60to 130° C. Furthermore, in order to maintain polymerization temperaturewithin this range, the polymerization system is cooled by a coolingapparatus. In addition, polymerization pressure is atmospheric pressureto 15 MPa, preferably 0.2 to 7 MPa, and most preferably 1 to 5 MPa.

When the present invention is applied to a multistage polymerization, itis preferable to maintain the hydrogen concentration of a gas phaseportion in the precedent stage at the condition not more than 30%. Evenif the hydrogen concentration is high enough to exceed 30%, there is noparticular problem in carrying out the production process of the presentinvention, but a large amount of hydrogen introduced into the subsequentstage increases the concentration of the olefin hydride (propane,ethane, or the like) produced in a gas phase reaction vessel and lowerspolymerization activity in the subsequent stage, and hence it is notpreferable that the hydrogen concentration is too high.

Furthermore, when a hydrogenation catalyst is added in a gas phasereaction vessel, it is preferable to have a step of adding apolymerization activity depressant in a polymerization reaction systemfrom the standpoints of improvement of powder properties and improvementof polymer properties.

The polymerization activity depressant used herein includes, forexample, an electron-donating compound, an active hydrogen-containingcompound, and an oxygen-containing compound gaseous at normaltemperatures and normal pressures, and the depressant generally has theaction of lowering the activity of an olefin polymerization catalyst.

The electron-donating compound includes alkoxysilanes, esters, ethers,and the like.

The active hydrogen-containing compound includes alcohols, water, andthe like.

The oxygen-containing compound gaseous at normal temperatures and normalpressures includes oxygen, carbon monoxide, carbon dioxide, and thelike.

The alkoxysilanes include tetrabutoxysilane, tetraethoxysilane,tetramethoxysilane, and the like.

The alcohols include methanol, ethanol, propanol, butanol, and the like.

The polymerization activity depressant is preferably an activehydrogen-containing compound or an oxygen-containing compound gaseous atnormal temperatures and normal pressures, is more preferably alcohols,oxygen or carbon monoxide, and is further preferably methanol, ethanol,propanol, butanol, oxygen or carbon monoxide.

Polymerization activity depressants may be used singly or in acombination of two or more kinds.

[Prepolymerization]

Before polymerization step a small amount of an olefin may bepolymerized (hereinafter referred to as prepolymerization) to form aprepolymerization catalyst component. As examples of an olefin to beprepolymerized, there can be shown ethylene, propylene, 1-butene,1-pentene, 1-hexene, 1-octene, 1-decene, 4-methyl-1-pentene,3-methyl-1-pentene, styrene, butadiene, isoprene, 1,4-hexadiene,dicyclopentadiene, 5-ethylidene-2-norbornene, and the like. The amountof an olefin to be prepolymerized is usually 0.1 to 200 g per g of thecatalyst component. As a method for the prepolymerization, there arecited publicly known methods such as a method of feeding a small amountof an olefin in the presence of the catalyst component and an organicaluminum compound and carrying out prepolymerization in slurry state byuse of a solvent. As a solvent used in prepolymerization, there arecited inert hydrocarbons such as propane, butane, isobutane, pentane,isopentane, hexane, heptane, octane, cyclohexane, benzene, toluene andthe like, and liquid olefins, and they may be used in a mixture of twoor more kinds. In addition, slurry concentration in prepolymerization isusually 1 to 500 g and preferably 3 to 150 g as the weight of catalystcomponent contained in 1 L of a solvent.

The amount of an organic aluminum compound used in prepolymerization is0.1 to 700 moles per mole of a transition metal atom contained in thecatalyst component, preferably 0.2 to 200 moles, and more preferably 0.2to 100 moles. In prepolymerization, an electron donor such as analkoxysilicon compound or the like may be present as needed. The amountof an electron donor used is preferably 0.01 to 400 moles per mole of atransition metal atom contained in the catalyst component, morepreferably 0.02 to 200 moles, further more preferably 0.03 to 100 moles.

Prepolymerization temperature is usually −20 to +100° C. and preferably0 to +80° C. In addition, prepolymerization time is usually 2 minutes to15 hours.

EXAMPLES

Hereinafter, the present invention is explained by way of Examples andComparative Examples. Measurements and evaluations of physicalproperties were carried out by the undermentioned methods.

(1) Limiting Viscosity (unit: dl/g)

By use of Ubbelohde viscometer, reduced viscosities were measured atthree concentrations of 0.1, 0.2 and 0.5 g/dl under the conditions oftetralin solvent and temperature: 135° C. Subsequently, limitingviscosity was obtained by extrapolation method of plotting the reducedviscosities to the concentrations and extrapolating the concentrationsto zero, in accordance with the calculation method disclosed in “PolymerSolution, Polymer Experimental Study 11” (published by Kyoritsu ShuppanCo., Ltd. in 1982), page 491.

(2) Copolymerized Portion Content (unit: weight %)

The copolymerized portion content X (weight %) produced in the firststage copolymerization step was calculated by the undermentionedformula.

X=(Pb−Pa)/Pb×100

Pa: Polymer weight per hour discharged from the third stage propylenepolymerization stepPb: Polymer weight per hour discharged from the first stagecopolymerization step(3) Limiting Viscosity (unit: dl/g) of Polymer Produced in CopolymerizedPortion

Limiting viscosity [η]a (dl/g) of the polymer component produced in thethird stage propylene polymerization step, and limiting viscosity[η]_(b) (dl/g) of the polymer component produced in the first stagecopolymerization step were calculated by the undermentioned formulas.

[η]a=[η]1

[η]b=([η]2−[η]a×(1−X/100))/(X/100)

[η]1: Limiting viscosity (dl/g) of the polymer after the third stagepropylene polymerization step[η]2: Limiting viscosity (dl/g) of the polymer after the first stagecopolymerization step

Example 1 Preparation of Titanocene Compound Solution

The inside of a flask having 1 L inner volume was replaced withnitrogen. Into this vessel 4.5 g of dicyclopentadienyltitaniumdichloride (manufactured by KANTO CHEMICAL CO., INC.) and 928 mL ofhexane were charged and at the same time stirred at room temperature,and 72 millimoles of triethyl aluminum was charged to obtain a solution.This solution was further diluted with hexane.

[Prepolymerization]

Into an autoclave made of SUS having 3 L inner volume and fitted with astirrer, 1.5 L of n-hexane sufficiently subjected to dehydration anddegasification treatments, 30 millimoles of triethyl aluminum, and 3.0millimoles of cyclohexylethyldimethoxysilane were charged. Therein 16 gof a solid catalyst component, which was prepared by a method same asthat of Example 1 of Japanese patent application No. 2008-277945, wasadded, 32 g of propylene was continuously fed in about 40 minutes whilekeeping the temperature in the autoclave at about 3 to 10° C., andprepolymerization was carried out. Subsequently, the prepolymerizedslurry was transferred to an autoclave made of SUS having 200 L innervolume and fitted with a stirrer, and 132 L of liquid butane was addedto form a prepolymerization catalyst component slurry.

By use of the prepolymerization catalyst component slurry prepared asmentioned above, three stage propylene homopolymerizations were carriedout respectively in different reactors to produce polypropyleneparticles. Subsequently, in the presence of the polypropylene particles,one stage copolymerization of propylene and ethylene was carried out toproduce a propylene-ethylene block copolymer. Hereinafter, eachpolymerization stage is explained.

[The First Stage Propylene Polymerization (Liquid Phase PolymerizationReaction)]

By use of a Bessel type reactor having 163 L inner volume and fittedwith a stirrer, homopolymerization of propylene was carried out. Thatis, propylene, hydrogen, triethyl aluminum,cyclohexylethyldimethoxysilane, and the prepolymerization catalystcomponent slurry were continuously fed in the reactor. The reactionconditions were polymerization temperature: 73° C., stirring velocity:150 rpm, liquid level of the reactor: 44 L, feed rate of propylene: 25kg/hour, feed rate of hydrogen: 160 NL/hour, feed rate of triethylaluminum: 40.9 millimoles/hour, feed rate ofcyclohexylethyldimethoxysilane: 6.13 millimoles/hour, and feed rate ofthe prepolymerization catalyst component slurry (calculated in terms ofthe polymerization catalyst component): 0.481 g/hour. In the reactor theaverage residence time of the slurry was 0.74 hour, and the amount ofpolypropylene particles discharged was 5.4 kg/hour.

[The Second Stage Propylene Polymerization (Liquid Phase PolymerizationReaction)]

The slurry, which had undergone the above first propylenepolymerization, was continuously transferred to another reactor (Besseltype), and homopolymerization of propylene was further carried out. Inthis connection, feeding of propylene and hydrogen to the reactor wasnot carried out. The reaction conditions were polymerizationtemperature: 69° C., stirring velocity: 150 rpm, and liquid level of thereactor: 44 L. In the reactor the average residence time of the slurrywas 0.85 hour, and the amount of polypropylene particles discharged was10.1 kg/hour.

[The Third Stage Propylene Polymerization (Gas Phase PolymerizationReaction)]

The polypropylene particles obtained through the above second propylenepolymerization were continuously transferred to a fluidized bed reactorhaving 1.4 m³ inner volume and fitted with a stirrer, propylene andhydrogen were continuously fed to this reactor, and homopolymerizationof propylene was further carried out, while purging the excess gas so asto keep the pressure constant. Reaction conditions were polymerizationtemperature: 80° C., polymerization pressure: 1.8 MPa, circulating gasflow rate: 100 m³/hour, feed rate of propylene: 10 kg/hour, feed rate ofhydrogen: 900 NL/hour, and polymer particle hold amount in the fluidizedbed: 50 kg. In the reactor the average residence time of polymerparticles was 3.2 hour, the gas concentration ratio (mole %) ofhydrogen/(hydrogen+propylene) in the reactor was 9.1, the amount ofpolymer particles discharged was 15.6 kg/hour, and the limitingviscosity thereof was 0.99 dl/g.

[The First Stage Copolymerization (Gas Phase Polymerization Reaction)]

The polypropylene particles obtained through the above third propylenepolymerization were continuously transferred to another fluidized bedreactor having 1 m³ inner volume and fitted with a gas-dispersing boardand a stirrer; propylene, ethylene, and hydrogen were continuously fedto this reactor; and copolymerization of propylene and ethylene wascarried out, while purging the excess gas so as to keep the pressureconstant. Reaction conditions were polymerization temperature: 70° C.,polymerization pressure: 1.4 MPa, circulating gas flow rate: 140m³/hour, feed rate of propylene: 22.5 kg/hour, feed rate of ethylene:6.8 kg/hour, feed rate of hydrogen: 200 NL/hour, and polymer particlehold amount in the fluidized bed: 85 kg. Furthermore, to the bed portionwere added the above-mentioned titanocene compound solution in an amountcorresponding to 2.32 millimoles calculated in terms of titanocenemolecular weight and tetraethoxysilane in an amount of 0.50 molecalculated in terms of tetraethoxysilane molecular weight per mole oftriethyl aluminum fed to the first stage propylene polymerizationreactor. A bulk density of polymerized powder in a bed portion was 0.305g/cc. Moreover, to the reactor was added, as a polymerization activitydepressant, oxygen in an amount corresponding to 1.4 millimolescalculated in terms of oxygen molecular weight per mole of triethylaluminum fed to the first stage propylene polymerization reactor. In thereactor the average residence time of polymer particles was 4.2 hour; asthe gas concentration ratio (mole %) in the reactor,ethylene/(propylene+ethylene) was 23, andhydrogen/(hydrogen+propylene+ethylene) was 0.26; the amount of polymerparticles discharged was 20.3 kg/hour; the limiting viscosity of thecopolymerized portion was 5.6 dl/g; and the copolymerized portioncontent was 23 weight %.

Comparative Example 1

Except that the tetraalkoxysilane was not added, the polymer hold amountwas adjusted so as to give the same copolymerized portion content as inExample 1. In the reactor the average residence time of polymerparticles was 2.9 hour; as the gas concentration ratio (mole %) in thereactor, ethylene/(propylene+ethylene) was 27, andhydrogen/(hydrogen+propylene+ethylene) was 0.59; the limiting viscosityof the copolymerized portion was 4.9 dl/g; hydrogen concentration washigh; and the molecular weight of the copolymerized portion was low.

Comparative Example 2

Without charging the tetraalkoxysilane and the titanocene compoundsolution, polymerization was carried out while adjusting the polymerhold amount so as to give the same copolymerized portion content as inExample 1. In the reactor the residence time of polymer particles was3.9 hour; as the gas concentration ratio (mole %) in the reactor,ethylene/(propylene+ethylene) was 27, andhydrogen/(hydrogen+propylene+ethylene) was 1.5; the limiting viscositywas 3.5 dl/g; hydrogen concentration was high; and the molecular weightof the copolymerized portion was low.

1. A hydrogenation catalyst formed by contacting the undermentionedcomponent (A), the undermentioned component (B), and the undermentionedcomponent (C): component (A): a titanocene compound, component (B): asilicon compound represented by the undermentioned general formula [1]:Si(OR¹)₄  [1] , wherein R¹ stands for a hydrocarbon group having 1 to 20carbon atoms, and four R¹ may be same or different respectively, andcomponent (C): an alkyl metal compound.
 2. A process for producing anolefin polymer characterized by polymerizing an olefin in the presenceof hydrogen, the undermentioned component (A), the undermentionedcomponent (B), and the undermentioned component (D): component (A): atitanocene compound, component (B): a silicon compound represented bythe undermentioned general formula [1]:Si(OR¹)₄  [1] , wherein R¹ stands for a hydrocarbon group having 1 to 20carbon atoms, and four R¹ may be same or different respectively, andcomponent (D): a catalyst for olefin polymerization.
 3. A process forproducing an olefin polymer characterized by polymerizing an olefin inthe presence of hydrogen, the undermentioned component (A), theundermentioned component (B), the undermentioned component (C), and theundermentioned component (D): component (A): a titanocene compound,component (B): a silicon compound represented by the undermentionedgeneral formula [1]:Si(OR¹)₄  [1] , wherein R¹ stands for a hydrocarbon group having 1 to 20carbon atoms, and four R¹ may be same or different respectively,component (C): an alkyl metal compound, and component (D): a catalystfor olefin polymerization.
 4. The process for producing an olefinpolymer as set forth in claim 2, wherein the component (D) is formed bycontacting the undermentioned component (a) and the undermentionedcomponent (b): component (a): a solid component containing titanium,magnesium and a halogen, and component (b): an alkyl aluminum compound.5. The process for producing an olefin polymer as set forth in claim 2,wherein the component (D) is formed by contacting the undermentionedcomponent (a), the undermentioned component (b), and the undermentionedcomponent (c): component (a): a solid component containing titanium,magnesium and a halogen, component (b): an alkyl aluminum compound, andcomponent (c): an electron-donating compound.
 6. The process forproducing an olefin polymer as set forth in claim 5, wherein thecomponent (c) is a silicon compound represented by the undermentionedgeneral formula [2]:R² _(r)Si(OR³)_(4-r)  [2] , wherein R² stands for hydrogen atom, ahydrocarbon group having 1 to 20 carbon atoms, or a heteroatom-containing group, R³ stands for a hydrocarbon group having 1 to 20carbon atoms, and r stands for an integer of 0 to 3, and when plural R²are present, plural R² may be respectively same or different, and whenplural R³ are present, plural R³ may be respectively same or different.7. A process for producing an olefin polymer, which comprisespolymerizing an olefin in the presence of hydrogen and theundermentioned component (D), characterized by having a step of addingthe undermentioned component (A) into a polymerization reaction systemand a step of adding the undermentioned component (B): component (A): atitanocene compound, component (B): a silicon compound represented bythe undermentioned general formula [1]:Si(OR¹)⁴  [1] , wherein R¹ stands for a hydrocarbon group having 1 to 20carbon atoms, and four R¹ may be same or different respectively, andcomponent (D): a catalyst for olefin polymerization.
 8. A process forproducing an olefin polymer, which comprises having two or more olefinpolymerization steps different in olefin polymerization conditions andpolymerizing an olefin in the presence of hydrogen and theundermentioned component (D), characterized by having a step of addingthe undermentioned component (A) and a step of adding the undermentionedcomponent (B) into a polymerization reaction system in the second andsubsequent olefin polymerization steps: component (A): a titanocenecompound, component (B): a silicon compound represented by theundermentioned general formula [1]:Si(OR¹)₄  [1] , wherein R¹ stands for a hydrocarbon group having 1 to 20carbon atoms, and four R¹ may be same or different respectively, andcomponent (D): a catalyst for olefin polymerization.